Mountain Flax (Wharariki)
Phormium cookianum
Mountain flax (Phormium cookianum) is a hardy New Zealand plant. Learn more about wetland plants.
Image credit: Mountain flax (Phormium cookianum). Wikipedia
Quick Facts
| Scientific Name | Phormium cookianum |
|---|---|
| Height | 0.6–1.6 m (flower stalks up to 2 m) |
| Spread | 1–2 m (clumping habit) |
| Water Needs | Moderate; prefers moist, free-draining soil but tolerates dry periods |
| Light | Full sun to partial shade |
| Frost Tolerance | Low to moderate (tolerates light frost, protect from severe frost) |
| Salt Tolerance | High (excellent coastal/salt wind tolerance) |
| Growth Rate | Moderate to fast |
| Lifespan | Perennial (long-lived, clumps persist for decades) |
Climate Suitability
Phormium cookianum thrives in mild, coastal to montane climates across New Zealand. It is well-adapted to areas with high rainfall, strong winds, and salt spray, making it ideal for exposed sites. While tolerant of a range of conditions, it prefers regions with moderate temperatures and is less frost-hardy than Phormium tenax. Mountain flax is commonly found on cliffs, riverbanks, and wetland margins from sea level up to 1,300 meters.
| City | Suitability |
|---|---|
| Whangārei | Ideal |
| Auckland | Ideal |
| Hamilton | Ideal |
| Tauranga | Ideal |
| Rotorua | Ideal |
| Gisborne | Ideal |
| New Plymouth | Ideal |
| Napier | Ideal |
| Whanganui | Ideal |
| Palmerston North | Ideal |
| Wellington | Ideal |
| Nelson | Ideal |
| Christchurch | Moderate |
| Dunedin | Moderate |
| Invercargill | Moderate |
Growing Requirements
- Soil: Prefers moist, free-draining soils but tolerates poor, rocky, or sandy soils.
- Light: Grows best in full sun to partial shade.
- Water: Requires regular watering when establishing; drought-tolerant once mature.
- Spacing: Allow at least 1.5 meters between plants for mature spread.
- Fertilizer: Not usually necessary, but a light mulch in spring can promote growth.
Uses & Significance
- Weaving: Leaves are prized for weaving kete (baskets), whāriki (mats), and other traditional Māori crafts.
- Ornamental: Popular in landscaping for its graceful, arching leaves and tolerance of harsh conditions.
- Ecological: Provides habitat and food for native birds and insects; stabilizes soil and prevents erosion.
- Restoration: Used in wetland and riparian restoration projects.
Seasonal Care Calendar
Spring
- New growth emerges; apply mulch and remove old leaves.
Summer
- Water during dry spells; monitor for pests such as flax snails.
Autumn
- Remove spent flower stalks; divide clumps if needed.
Winter
- Minimal care required; protect young plants from severe frost.
Pruning
Remove dead or damaged leaves at the base as needed. Prune spent flower stalks after flowering. Avoid cutting into the central fan, as this can damage the plant. Pruning is best done in late winter or early spring before new growth begins.
Planting Guide
When to Plant
Best planted in spring or autumn when soil is moist and temperatures are mild.
Site Selection
- Choose a site with good drainage and full sun to partial shade.
- Ideal for coastal gardens, wetland edges, and slopes.
Planting Procedure
- Prepare soil by removing weeds and loosening the ground.
- Dig a hole just large enough for the root ball.
- Plant at the same depth as in the pot.
- Backfill and firm gently.
- Water in well and mulch to retain moisture.
Propagation
- Division: The easiest method. Divide established clumps in spring or autumn, ensuring each division has roots attached.
- Seed: Sow fresh seed in trays of seed-raising mix in spring. Germination can be slow and variable.
Cultural History
Known as wharariki to Māori, Phormium cookianum has been used for centuries for weaving and rope-making. Its softer, more flexible leaves are preferred for fine weaving compared to Phormium tenax. The plant features in Māori legends and is valued for its role in traditional crafts and as a resource for clothing, mats, and fishing lines. Today, it remains an important symbol of New Zealand’s natural and cultural heritage.
Pests & Diseases
- Generally pest-free, but may be affected by:
- Flax snails (Powelliphanta spp.)
- Scale insects and mealybugs
- Leaf spot and rust in humid conditions
- Ensure good air circulation and avoid waterlogging to prevent disease.
Bonus Tip
Plant Phormium cookianum on slopes or banks to help control erosion and add year-round interest to your garden.
Cultural Significance
Overview
Learn more about the cultural significance of native trees in Cultural Plants.